3. Without an axis tilt, the Earth will not have seasons because the amount of sunlight striking different places on the Earth would remain essentially constant at all times (with a slight variation due to the changing Earth - Sun distance).

4.
a. At full moon, you would see a new Earth from your home on the moon.  It would be daylight at your home, with the sun on your meridian and about a week until sunset.

b. At full moon, you would see full Earth from your home on the moon.  It would be midnight at your home, with about one week to go until sunrise.

c. You would see sunset at third quarter moon, at which time you would see first quarter Earth.

d. You would see sunrise at first quarter moon, at which time you would see third quarter Earth.

e. If you were on the Moon during a total lunar eclipse (as seen from Earth), you would see a total eclipse of the Sun.

f. If you were on the moon during a total solar eclipse (as seen from the Earth), you would see the small circular shadow of the Moon on the full Earth.

6.
a. I saw the Sun rise in the west.  This statement makes no sense because the Sun rises in the East - this cannot change unless the Earth rotation changes.

b. In South Africa, it's quite warm around the time of winter solstice and quite cool around the time of summer solstice.  This statement makes sense because the seasons in the Southern Hemisphere are opposite to those in the Northern Hemisphere.

c. January is the best month to ski in New Zealand.  This statement does not make sense (if snow skiing as opposed to water skiing) because it is summer in New Zealand in January.

d. It was midnight and the crescent Moon was on my meridian.  This statement does not make sense because only a full Moon can be on the meridian at midnight.

e. Tomorrow the Moon will be in first quarter phase, and today I saw a total lunar eclipse.  This statement does not make sense because a lunar eclipse can occur only at full Moon, which occurs a week after first quarter phase.

f. When I was a child living in southern Florida, I once saw a total solar eclipse from my home two years in a row.  This statement does not make sense because solar eclipses do not occur in the same location on Earth two years in a row.

g. I was up early and saw the full Moon rising just before sunrise.  This statement makes no sense because the full Moon rises around sunset.